Approximately 60% of total body weight is water. Adequate amounts of water must be consumed daily to ensure normal functioning of the body and to replenish lost fluids. Its also needed to absorb and digest nutrients, excrete wastes, maintain body temperature and blood circulation. Fluid balance is like energy balance. With dehydration, water loss exceeds intake through breathing when your activity level is low, most fluids are lost through the urine. When activity or temperature levels are high, most fluids are lost through sweat.